Unit 1 (K7/8) - Cellular Respiration/Lactate Metabolism

Question 1

What is cellular respiration?

Answer 1

This is a series of metabolic pathways that brings about the release of energy.

Question 2

What is phosphorylation?

Answer 2

This is where inorganic phosphate combines with low-energy ADP to form high energy ATP.

Question 3

What does phosphorylation do?

Answer 3

Makes a molecule more reactive. Often a step in a pathway can only proceed if a reactant becomes phosphorylated and energised.

Question 4

What is glycolysis?

Answer 4

The breakdown of glucose to pyruvate in the cytoplasm.

Question 5

What are the two stages within glycolysis?

Answer 5

The energy investment stage and the energy payoff stage.

Question 6

Why is ATP required in the energy investment stage of glycolysis?

Answer 6

For the phosphorylation of glucose and intermediates.

Question 7

In aerobic respiration which reaction occurs between glycolysis and the citric acid cycle?

Answer 7

Pyruvate is broken down into an acetyl group that combines with coenzyme A to form acetyl coenzyme A.

Question 8

Describe what happens in the citric acid cycle

Answer 8

1. Acetyl coenzyme A gives up its acetyl group which combines with oxaloacetate to form citrate.
2. Citrate is converted back into oxaloacetate in a series of enzyme-controlled steps which generate ATP and release carbon dioxide.

Question 9

Where does the citric acid cycle occur?

Answer 9

In the matrix of the mitochondria.

Question 10

How is NADH formed in both glycolysis and the citric acid cycle?

Answer 10

Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD which forms NADH.

Question 11

What happens to hydrogen and electrons from NADH?

Answer 11

They are passed to the electron transport chain on the inner mitochondrial membrane.

Question 12

Describe how ATP is made from the electron transport chain?

Answer 12

1. Electrons are pumped along the electron transport chain and release energy.
2. The energy is used to pump hydrogen ions across the inner mitochondrial membrane towards protein ATP synthase which creates ATP.

Question 13

What happens to the hydrogen and electrons at the end of the electron transport chain?

Answer 13

They combine with oxygen to form water.

Question 14

When does lactate metabolism occur?

Answer 14

When there is not sufficient oxygen to support the electron transport chain. Therefore, this causes pyruvate to be converted to lactate.

Question 15

In which cells is lactate metabolism common?

Answer 15

In muscle cells during vigorous exercise.

Question 16

How is pyruvate converted into lactate?

Answer 16

This involves the transfer of hydrogen from the NADH produced during glycolysis to pyruvate in order to produce lactate.

Question 17

Why is the regeneration of NAD important?

Answer 17

This is needed to maintain ATP production.

Question 18

What happens after exercise is complete and there is enough oxygen again?

Answer 18

This allows respiration to provide the energy to convert lactate back to pyruvate and glucose in the liver.

Question 19

What happens when lactate accumulates?

Answer 19

Muscle fatigue occurs.

Question 20

Describe the characteristics of slow-twitch muscle fibres

Answer 20

1. Contract relatively slowly but can sustain contractions for longer.
2. Rely on aerobic respiration to generate ATP.
3. Have many mitochondria.
4. Have a large blood supply.
5. High concentration of myoglobin.
6. Fats as a major storage fuel.

Question 21

Describe the characteristics of fast twitch muscle fibres

Answer 21

1. Contract relatively quickly over short periods.
2. Generate ATP through glycolysis.
3. Have few mitochondria
4. Small blood supply.
5. Glycogen as major storage fuel.

Question 22

What activities require slow twitch muscle fibres?

Answer 22

Endurance activities such as long distance running or cycling.

Question 23

What activities require fast twitch muscle fibres?

Answer 23

Sprinting or weight-lifting.